A very wide range of different production processes are known for the production of hollow bodies of thermoplastic material, for example extrusion blow molding, deep drawing or injection molding. In the extrusion blow molding process the hollow body can be seamlessly produced for example from a single tubular preform. It will be noted that there is also the possibility of dividing up a tubular preform in respect of length into webs, placing the webs separately in a two-part or multi-part tool and expanding or shaping the webs within the tool by means of a reduced pressure or by the action of gas pressure.
Particularly in the production of technical components such as fuel tanks which are produced in the above-described manner in one or more parts from thermoplastic material, it is necessary for various built-in fitment components or attachments to be fixed to the hollow body. That can be effected in the first heat in the production procedure or also subsequently. If the hollow body is intended to accommodate the built-in fitment components in its interior, it is frequently necessary, because of the size of those components, for them to be introduced into the hollow body in the production of the latter. The built-in fitment components and attachments which are to be installed or attached can be clipped or welded to the hollow body, in which case the welding operation can be effected in production of the hollow body in the first heat or subsequently in the second heat, for example by friction welding or welding with a heat reflector.
Limits are often imposed on positively locking anchorage of a built-in fitment component in the interior of the hollow body, by virtue of the process for the production thereof. For example, when producing hollow bodies by an extrusion blow molding process, it is only limitedly possible to provide in the contour of the hollow body undercut configurations which permit built-in fitment components to be locked to the wall of the hollow body in positively engaging relationship. For that reason recourse is frequently had to welding as the joining procedure.
However welding the components together suffers from the disadvantage that the plastic materials to be joined must form a mutually weldable material pairing. That limits the choice of the built-in fitment components or attachments for the hollow body.
By way of example in the production of fuel tanks of plastic material that can represent a far-reaching limitation as certain plastic materials, in the presence of fuel, are sources or are permeable for hydrocarbons. Therefore for certain conduits and valves it is necessary to choose a material which from the outset excludes the possibility of welding to the tank or the hollow body.
Therefore the object of the invention is to provide a process for the production of an article enclosing built-in fitment components in the form of a hollow body of thermoplastic material, which permits particularly simple and secure fixing of built-in fitment components in the hollow body in the course of the production thereof.
A further object of the invention is to provide a plastic hollow body to which built-in fitment components or attachments are joined in positively locking relationship in a particularly simple fashion.